1. Technical Field
Embodiments of the present invention are related to the field of communication devices, and in particular, to multicarrier communication devices.
2. Description of Related Art
Many modern digital communication systems, including wireless local-area networks (WLANs), are using symbol-modulated orthogonal subcarriers as a modulation scheme to help signals survive in environments having multipath reflections and/or strong interference. Orthogonal frequency-division multiplexing (OFDM) is an example of a multicarrier transmission technique that uses symbol-modulated orthogonal subcarriers to transmit information within an available spectrum. A multiple access scheme based on the OFDM includes orthogonal frequency division multiple access (OFDMA). In OFDMA a subset of the entire set of orthogonal subcarriers is assigned to a particular user. This enables an OFDMA system to have multiple simultaneous users, each assigned to a different subset.
Phase noise may be interpreted as a random parasitic phase modulation in an oscillator's signal, which ideally would be a unique sinusoidal carrier with constant amplitude and frequency. A signal which is demodulated in the receiver station of a multicarrier system, such as an OFDM or OFDMA system, may have superimposed on it phase noise of all the local oscillators (LOs) in the chain between it and a modulator. Phase noise in OFDM and OFDMA systems basically have two effects: a phase error common to all OFDM subcarriers called the common phase error (CPE) and inter-carrier interference (ICI). ICI may be characterized as a spilling of the spectrum of subcarrier signals into adjacent subcarriers. The ICI component is a factor in limiting the use of higher order (Quadrature Amplitude Modulated) QAM constellations; hence, preventing achievement of higher data rates.